Method for injection moulding an external housing of an object, object and apparatus for injection moulding

• US 8,936,200 B2
• Filed: 11/11/2009
• Issued: 01/20/2015
• Est. Priority Date: 11/11/2009
• Status: Active Grant

• Current Assignee: Balluff Verwaltungsges mbH
• Original Assignee: Balluff Verwaltungsges mbH
• Inventors: Schimmel, Johannes Adelbert
• Primary Examiner(s): Frech, Karl D
• Application Number:
  US13/509,358
• Publication Number:
  US 20120248199A1
• Time in Patent Office: 1,896 Days
• Field of Search: 235/380, 235/375, 235/492, 235/487, 235/488
• US Class Current: 235/492
• CPC Class Codes: B29C 2045/14131 using positioning or centering means forming part of the insert
• CPC Class Codes: B29C 2045/14147 using pins or needles penetrating through the insert
• CPC Class Codes: B29C 2045/14967 Injecting through an opening of the insert
• CPC Class Codes: B29C 2045/14975 the injection nozzle penetrating through the insert
• CPC Class Codes: B29C 45/14073 using means being retractable during injection
• CPC Class Codes: B29C 45/14639 for obtaining an insulating effect, e.g. for electrical components
• CPC Class Codes: B29C 45/14819 the inserts being completely encapsulated
• CPC Class Codes: H01L 21/565 Moulds
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A method for injection molding an external housing of an object including an electronic assembly includes interposing the assembly between a first half-mold and a second half-mold of an open injection mold and closing the first half-mold and the second half-mold to define an injection cavity containing the assembly. Plastic is injected in the cavity to mold said external housing. The step of interposing includes positioning, before the injection of plastics, the assembly on movable support means associated with the mold, the support means being arranged on an extended position, and disengaging the support means from the assembly before the plastic is cured such as to manufacture the external housing in an only one shot manufacturing process. This way, plastic of the external housing is integrally molded and devoid of discontinuity points.

Claims

1. A method for injection moulding an external housing of an object provided with a mounting through hole, in particular a high temperature or harsh environment RFID tag or wireless device, said object comprising an electronic assembly provided with a further mounting through hole;

said method comprising the steps of;

interposing said electronic assembly between a first half-mould and a second half-mould of an open injection mould;

closing said first half-mould and said second half-mould to define an injection cavity of a mould, containing said assembly; and

injecting plastics in said cavity wherein said interposing step comprises positioning said assembly on movable support means in an extended position, said support means being associated with said mould, the method further comprising the step of disengaging said support means from said assembly before said plastics are cured such as to manufacture said external housing in only a one shot manufacturing process, plastics of said external housing being integrally moulded and devoid of discontinuity points, wherein the method further comprises;

providing an injection nozzle on a protrusion of a half-mould facing a further protrusion provided on the other half-mould and defining an injection sprue volume therebetween; and

positioning said injection sprue volume inside said further mounting through hole for injecting said plastics from said injection sprue volume towards said first half-mould and said second half-mould at the same time, such that said further mounting through hole is encapsulated with plastics, thus creating said mounting through hole during injection.

2. The method according to claim 1, wherein said step of disengaging said support means from said assembly comprises housing said support means in seat means obtained in said mould in a retracted position.

3. The method according to claim 1, wherein said positioning step comprises inserting said support means in at least a through hole of said assembly, before closing said mould.

4. The method according to claim 3, wherein said inserting step comprises fitting said support means in said assembly and deforming a portion of said assembly around said through hole by an interference fit.

5. The method according to claim 1, wherein said support means comprises first movable support means associated with said first half-mould and housed in first seat means of said first half-mould in a first retracted position, said positioning step further comprises inserting said first supporting means in at least a through hole of said assembly, said first support means being arranged on a first extended position in which said first support means are positioned out of said first seat means inside said cavity.

6. The method according to claim 5, wherein said support means comprises second movable support means associated with said second half-mould and housed in second seat means of said second half-mould in a second retracted position, said positioning step further comprises clamping said assembly in a injection configuration between said first support means on said first extended position and said second support means on a second extended position, in which said second support means are positioned out of said second seat means inside said cavity, before injecting said plastics.

7. The method according to claim 6, wherein said clamping step comprises maintaining said assembly distanced from first walls of said first half-mould and from second walls of said second half-mould.

8. The method according to claim 6, wherein said step of disengaging said support means comprises disengaging firstly said second support means from said assembly, maintaining said first support means in said through hole, when said injected plastics reach a zone of said cavity interposed between said second half-mould and said assembly such that said injection configuration is guaranteed.

9. The method according to claim 8, wherein said disengaging step firstly is achieved when said cavity is 90% filled of plastics.

10. The method according to claim 8, wherein said disengaging firstly is achieved when said cavity is 94% filled of plastics.

11. The method according to claim 8, wherein said disengaging step firstly comprises clearing said cavity from said second support means or from said first support means, and housing said whole second support means or said whole first support means in said second seat means or in said first seat means.

12. The method according to claim 8, wherein said method further comprises disengaging lastly said first support means from said through hole, after said second support means have been already disengaged, when said plastics injected in said cavity fill said cavity of an amount such that said injection configuration is guaranteed.

13. The Method according to claim 12, said method further comprising filling said through hole with said plastics before said plastics are completely cured.

14. The method according to claim 12, wherein said step of disengaging lastly said first support means is achieved when said cavity is 95% filled of plastics.

15. The method according to claim 12, wherein said step of disengaging lastly comprises clearing said cavity from said first support means, and housing said whole first support means in said first seat means.

16. The method according to claim 6, wherein said step of disengaging said support means comprises disengaging firstly said first support means from said assembly, said second support means still supporting said assembly, when said plastics injected in said cavity reach a zone of said cavity interposed between said first half-mould and said assembly such that said injection configuration is guaranteed.

17. The method according to claim 16, wherein said method further comprises disengaging lastly said second support means, after said first support means have been already disengaged, when said plastics injected in said cavity fill said cavity of an amount such that said injection configuration is guaranteed.

18. The method according to claim 17, wherein said step of disengaging lastly said second support means is achieved when said cavity is 99% filled of plastics.

19. The method according to claim 1, wherein said method further comprises filling a volume of said cavity between said first half-mould and said assembly and a volume of said cavity between said second half-mould and said assembly with respective amounts of plastics which are approximately the same in the same time.

20. The method according to claim 1, wherein said injecting step comprises arranging a midpoint of the height of said injection sprue volume, along a symmetry axis of said injection sprue volume, substantially at a midpoint of the height of said further mounting through hole, along a symmetry axis of said injection sprue volume, such as to guarantee filling said cavity at the centre of said further mounting through hole.

21. An object comprising:

an RFID tag electronic assembly encapsulated in an external housing of plastics, wherein said external housing is made of plastics integrally moulded and devoid of discontinuity points, said assembly comprising at least a through hole, said through hole being filled with plastics and wherein said object comprises a mounting through hole suitable for housing mounting fixing means, said assembly being provided with a further mounting through hole in correspondence to said mounting through hole, said external housing encapsulating said further mounting through hole with a region of plastics integrally moulded devoid of discontinuity points, wherein said plastics is a thermally resistant plastics having a survival temperature in the range approximately of 220°

C. to 300°

C.

22. The object according to claim 21, wherein said thermally resistant plastics is a Teflon®

or a Noryl®

based compound or a Ryton®

PPS based compound.

23. An apparatus for injection moulding plastics to provide an external housing of an object with a mounting through hole comprising an RFID tag electronic assembly being provided with a further mounting through hole, said apparatus comprising:

a first half-mould cooperating with a second half-mould to define a mould having an injection cavity, said apparatus further comprising support means associated to said mould movable between an extended position, in which said support means is positioned inside said cavity out of seat means of said mould and holds said assembly during injection of plastics, and a retracted position, in which said support means is housed in said seat means and is disengaged from said assembly, such that said plastics encapsulate said assembly providing an external housing of integrally moulded plastics devoid of discontinuity points,

wherein said apparatus comprises an injection nozzle on a protrusion of a half-mould facing a further protrusion provided on the other half-mould and defining an injection sprue volume therebetween in a closed position of said mould;

said injection sprue volume being suitable for being positioned inside said further mounting through hole such as to inject said plastics from said injection sprue volume at the same time towards said first half-mould and said second half-mould, encapsulating said further mounting through hole with plastics and creating said mounting through hole in said external housing during injection.

24. The apparatus according to claim 23, wherein said support means comprises first support means associated to said first half-mould and second support means associated to said second half-mould;

said first support means being movable between a first extended position, in which said first support means is positioned inside said cavity out of first seat means of said first half-mould and a first retracted position, in which said first support means is housed in said first seat means disengaged from said assembly;

said second support means being movable between a second extended position in which said second support means is positioned inside said cavity out of second seat means of said second half-mould and a second retracted position in which said second support means is housed in said second seat means disengaged from said assembly.

25. The apparatus according to claim 24, wherein said first support means in said first extended position and said second support means in said second extended position are suitable for clamping, during injection of plastics, said assembly, maintaining said assembly in an injection configuration, distanced from first walls and second walls of respective first half-mould and second half-mould.

26. The apparatus according to claim 25, wherein said first support means comprises a first pin and said second half-mould comprises a second pin defining a pair of pins, said first pin being aligned and facing said second pin for clamping said assembly therebetween in said injection configuration.

27. The apparatus according to claim 26, wherein said first pin and/or said second pin have a tapered end, a portion of said first pin comprising said tapered end being suitable to be fit in a correspondent through hole of said assembly by an interference fit.

28. The apparatus according to claim 27, wherein said first pin and said second pin have a width greater than or equal to the width of said corresponding through hole.

29. The apparatus according to claim 25, wherein said first support means comprises a plurality of first pins and said second support means comprises a plurality of second pins defining a plurality of pair of pins, each first pin of said first plurality being aligned and facing a corresponding second pin of said second plurality for clamping said assembly therebetween in said injection configuration.

30. The apparatus according to claim 24, further comprising first driving means of said first support means and second driving means of said second support means to drive said first support means and said second support means independently one another.

31. The apparatus according to claim 23, wherein said first support means and second support means in said first retracted position and second retracted position are wholly housed in said first seat means and said second seat means thereby clearing said injection cavity from said support means.

32. The apparatus according to claim 23, wherein said injection sprue volume is externally delimited by an open lateral border, said injection sprue volume being positioned centered in the middle of said further mounting through hole so that said plastics is injected from said lateral border towards said first half-mould and second half-mould with amounts which are approximately the same in the same time.

33. The apparatus according to claim 23, wherein a midpoint of the height of said injection sprue volume, along a symmetry axis of said injection sprue volume, is arranged substantially at a midpoint of the height of said further mounting through hole along a symmetry axis of said further mounting through hole.

34. The apparatus according to claim 33, wherein said injection sprue volume and said further mounting through hole have the same symmetry axis.